Semiconductor device having contact feature and method of fabricating the same

ABSTRACT

A method including providing a device including a gate structure and a source/drain feature adjacent to the gate structure. An insulating layer (e.g., CESL, ILD) is formed over the source/drain feature. A trench is etched in the insulating layer to expose a surface of the source/drain feature. A semiconductor material is then formed in the etched trench on the surface of the source/drain feature. The semiconductor material is converted to a silicide.

BACKGROUND

The electronics industry has experienced an ever-increasing demand forsmaller and faster electronic devices which are simultaneously able tosupport a greater number of increasingly complex and sophisticatedfunctions. Accordingly, there is a continuing trend in the semiconductorindustry to manufacture low-cost, high-performance, and low-powerintegrated circuits (ICs). Thus far these goals have been achieved inlarge part by scaling down semiconductor IC dimensions (e.g., minimumfeature size) and thereby improving production efficiency and loweringassociated costs. However, such scaling has also introduced increasedcomplexity to the semiconductor manufacturing process. Thus, therealization of continued advances in semiconductor ICs and devices callsfor similar advances in semiconductor manufacturing processes andtechnology.

For example, fabrication of vertical interconnects becomes morechallenging as feature sizes continue to decrease. For example, formingcontacts to transistor features such as source, drain, or gate may bedifficult to achieve without impacting contact resistance and/or seriesresistance of the device. In particular, as devices are scaled, thetotal on-scaled resistance may be determined in large part by the seriesresistance in forming vertical contacts to the transistor features.Thus, the current devices and methods of forming thereof may not besatisfactory in all aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 2 is perspective view of an embodiment of a FinFET device accordingto one or more aspects of the present disclosure;

FIG. 1 is a flow chart of a method of fabricating a semiconductor deviceincluding a contact feature, in accordance with some embodiments;

FIGS. 3A, 3B, 4A, 4B, 5A, 5B, 6, 7, 8, 9, 10 and 11 illustratecross-sectional embodiments according to various steps of the method ofFIG. 1, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. The spatially relativeterms are intended to cover different orientations of the deviceincluding the features. Still further, when a number or a range ofnumbers is described with “about,” “approximate,” and the like, the termis intended to encompass numbers that are within a reasonable rangeincluding the number described, such as within +/−10% of the numberdescribed or other values as understood by person skilled in the art.For example, the term “about 5 nm” encompasses the dimension range from4.5 nm to 5.5 nm.

The present disclosure is generally related to semiconductor devices,and more particularly to field-effect transistors (FETs), such as planarFETs or three-dimensional fin-like FETs (FinFETs). It is an objective ofthe present disclosure to provide vertical interconnect features (e.g.,via contact features) for connecting device-level contact features(e.g., source/drain features) with additional interconnect features insemiconductor devices.

A device relevant to the present disclosure may include a P-typemetal-oxide-semiconductor FinFET device or an N-typemetal-oxide-semiconductor FinFET device. The FinFET device may be adual-gate device, tri-gate device, bulk device, silicon-on-insulator(SOI) device, and/or other configuration. One of ordinary skill mayrecognize other embodiments of semiconductor devices that may benefitfrom aspects of the present disclosure. For example, some embodiments asdescribed herein may also be applied to gate-all-around (GAA) devices,Omega-gate (ω-gate) devices, or Pi-gate (Π-gate) devices. As above, inother embodiments, the device relevant to and fabricated by aspects ofthe present disclosure may be a planar device.

In semiconductor device fabrication, lithography patterning and etchingprocesses are typically implemented to form a contact trench (or acontact hole or opening) over a device-level feature (e.g., a metal gatestack, a source/drain feature) before depositing a conductive materialin the contact trench to form a contact feature to the transistorelement—i.e., to a source/drain (S/D) feature or region. In formingcontact trenches (or holes or openings) there may be a certain amount ofover-etching that is difficult to control and/or desired to ensureremoval of the dielectric material. Under-etching a trench that extendsto the source/drain region results in an incomplete, high resistance, oreven omitted contact. However, the over-etching can impact thesource/drain region and thus, device performance. For example, etchinginto the semiconductor material removes a portion of the source/drainregion and thus, a portion of the available carriers. In someembodiments, loss of material in the source/drain region will introducecontact resistance and/or series resistance from the source/drain regionand/or contact thereto. Thus, for these and other reasons, it isdesirable to improve methods for forming a contact feature to thesource/drain region of the device.

FIG. 1 illustrates an embodiment of a method 100 for forming asemiconductor device according to various aspects of the presentdisclosure. The method 100 is merely an example and is not intended tolimit the present disclosure beyond what is explicitly recited in theclaims. Additional operations can be provided before, during, and afterthe method 100, and some operations described can be replaced,eliminated, or moved around for additional embodiments of the method.The method 100 is described below in conjunction with FIGS. 2-11, whichillustrate a portion of the semiconductor device 200 during intermediatesteps of the method 100. FIGS. 3A, 4A, 5A, and 6-11 are cross-sectionalviews of the device 200 taken along dashed line AA′ as illustrated inFIG. 2. FIGS. 3B, 4B, and 5B are cross-sectional views of the device200′, which is an embodiment of the device 200, taken along dashed lineAA′ as illustrated in FIG. 2. The device 200 may be an intermediatedevice fabricated during processing of an IC, or a portion thereof, thatmay comprise static random-access memory (SRAM) and/or other logiccircuits, passive components such as resistors, capacitors, andinductors, and active components such as p-type FETs (PFETs), n-typeFETs (NFETs), FinFETs, metal-oxide semiconductor field effecttransistors (MOSFETs), complementary metal-oxide semiconductor (CMOS)transistors, bipolar transistors, high voltage transistors, highfrequency transistors, and/or other memory cells The present disclosureis not limited to any particular number of devices or device regions, orto any particular device configurations. For example, again, thoughcertain examples of the device 200 as illustrated is a three-dimensionalFinFET device, the present disclosure may also provide embodiments forfabricating planar FET devices.

The method 100 operation 102 includes providing a device having a gatestructure and a source/drain feature also referred to as a source/drainregion. The device in some embodiments has a three-dimensional activeregion (hereafter referred to as fin) disposed over a substrate. Thedevice further includes a gate structure disposed over the fin;source/drain (S/D) features disposed over, on, or in the fin; andvarious dielectric layer(s) providing suitable insulating and mechanicalsupport functions. In an embodiment, the gate structures are metal gate(MG) structures having a gate electrode comprising metal and anunderlying gate dielectric. In an embodiment, the S/D features areepitaxially grown regions that are suitably doped to provide relevantfunctionality (e.g., p-type or n-type). For example, source/drainregions may, for example, be formed with in-situ P-type doping duringepitaxial growth or by implanting P-type dopants after epitaxial growthor by implanting P-type doping into a region of the substrate/fin, andthus may be referred to as P-type source/drain regions. P-typesource/drain regions may be used with the associated gate structureformed to establish a PFET. A P-type source/drain region may be formedby forming positively charged particles in the source/drain region bydoping. For example, a P-type is element is introduced to thesemiconductor to generate free hole (by “accepting” electron fromsemiconductor atom and “releasing” hole at the same time). P-typedopants may include but are not limited to, for example, boron (B),indium (In) and gallium (Ga). For example, source/drain regions mayinclude silicon germanium and/or any other now known or later developedstressor for generating a compressive stress in the channel of the PFETto enhance the mobility of the holes created by the P-type dopant.

Additionally or alternatively, source/drain regions may be formed within-situ N-type doping during epitaxial growth or by implanting N-typedopants after epitaxial growth or by implanting N-type doping into aregion of the substrate/fin, and thus may be described herein as N-typesource/drain regions. N-type source/drain regions may be formed inassociated with a gate structure to establish an NFET. An N-typesource/drain region may be formed by forming negatively chargedelectrons in the source/drain region by doping. For example, an N-typeis element is introduced to the semiconductor to generate free electron(by “donating” electron to semiconductor). Common N-type dopants includephosphorous (P), arsenic (As), antimony (Sb) and in gallium arsenic(GaAs): sulphur (S), selenium (Se), tin (Sn), silicon (Si), and carbon(C). N-type dopants may include, for example, phosphorous (P), arsenic(As), antimony (Sb). Source/drain regions may include, for example,silicon phosphorus (SiP), and/or any other now known or later developedmaterial for forming an N-type source/drain region.

Continuing the discussion from above, in the example of FIG. 2illustrated is a FinFET device 200. The FinFET device 200 includes oneor more fin-based, multi-gate field-effect transistors (FETs). TheFinFET device 200 includes a substrate 202, at least onethree-dimensional active region, commonly referred to as a fin, element204 extending from the substrate 202, isolation regions 206, and a gatestructure 208 disposed on and around the fin-element 204. Insulatinglayer(s) 210 are formed over the substrate 202.

The substrate 202 may be a semiconductor substrate such as a siliconsubstrate. The substrate 202 may include various layers, includingconductive or insulating layers formed on a semiconductor substrate. Thesubstrate 202 may include various doping configurations depending ondesign requirements as is known in the art. The substrate 202 may alsoinclude other semiconductors such as germanium, silicon carbide (SiC),silicon germanium (SiGe), or diamond. Alternatively, the substrate 202may include a compound semiconductor and/or an alloy semiconductor.Further, in some embodiments, the substrate may include an epitaxiallayer (epi-layer), the substrate may be strained for performanceenhancement, the substrate may include an SOI structure, and/or thesubstrate may have other suitable enhancement features.

The fin 204, like the substrate 202, may comprise silicon or anotherelementary semiconductor, such as germanium; a compound semiconductorincluding silicon carbide, gallium arsenide, gallium phosphide, indiumphosphide, indium arsenide, and/or indium antimonide; an alloysemiconductor including SiGe, GaAsP, AlInAs, AlGaAs, InGaAs, GaInP,and/or GaInAsP; or combinations thereof. The fins 204 may be fabricatedusing suitable processes including photolithography and etch processes.The photolithography process may include forming a photoresist layer(resist) overlying the substrate (e.g., on silicon), exposing the resistto a pattern, performing post-exposure bake processes, and developingthe resist to form a masking element including the resist. In someembodiments, patterning the resist to form the making element may beperformed using an electron beam (e-beam) lithography process. Themasking element may then be used to protect regions of the substratewhile an etch process forms recesses into the silicon layer, therebyleaving an extending fin 204. The recesses may be etched using a dryetch (e.g., chemical oxide removal), a wet etch, and/or other suitableprocesses. Numerous other embodiments of methods to form the fins 204 onthe substrate 202 may also be used.

Each of the plurality of fins 204 include a source region 205 and adrain region 207 where the source/drain regions 205, 207 are formed in,on, and/or surrounding the fin 204. The source/drain regions 205, 207may be epitaxially grown in, on or over the fins 204. As discussedabove, the source/drain regions 205, 207 may provide a PFET or NFET andbe suitably composed. A channel region of a transistor is disposedwithin the fin 204, underlying the gate structure 208, along a planesubstantially parallel to a plane defined by section AA′ of FIG. 2. Thechannel region of the fin 204 may be differently comprised than thesource/drain regions 205, 207 (e.g., silicon and SiGe, silicon and Ge).In some embodiments, the channel region of the fin 204 may have the samecomposition as the source/drain regions 205, 207 (e.g., silicon,germanium).

Each of the S/D regions 205, 207 may be suitable for forming a p-typeFinFET device (e.g., a p-type epitaxial material) or alternatively, ann-type FinFET device (e.g., an n-type epitaxial material). As discussedabove, in an embodiment, the p-type epitaxial material may include oneor more epitaxial layers of silicon germanium (epi SiGe) doped with ap-type dopant such as boron, germanium, indium, and/or other p-typedopants. In an embodiment, the n-type epitaxial material may include oneor more epitaxial layers of silicon (epi Si) or silicon carbon (epi SiC)doped with an n-type dopant such as arsenic, phosphorus, and/or othern-type dopant. In some embodiments, the epitaxial material of thesource/drain regions 205, 207 is germanium.

The isolation regions 206 disposed between fins 204 may be shallowtrench isolation (STI) features. Alternatively, a field oxide, a LOCOSfeature, and/or other suitable isolation features may be implemented onand/or within the substrate 202. The isolation regions 206 may becomposed of such as tetraethylorthosilicate (TEOS), silicon oxide,silicon nitride, silicon oxynitride, a low-k dielectric material, dopedsilicon oxide such as borophosphosilicate glass (BPSG), phosphosilicateglass (PSG), fluorine-doped silicate glass (FSG), boron doped silicateglass (BSG), other suitable dielectric materials, combinations thereof,and/or other suitable material known in the art. In an embodiment, theisolation structures are STI features and are formed by etching trenchesin the substrate 202. The trenches may then be filled with isolatingmaterial(s), followed by a chemical mechanical polishing (CMP) processand subsequent etch-back processes. However, other embodiments arepossible. In some embodiments, the isolation regions 206 may include amulti-layer structure, for example, having one or more liner layers.

The gate structure 208 includes a gate stack including a gate dielectriclayer, and one or more conductive layers (e.g., polysilicon or metallayer(s)) formed over the gate dielectric layer. In some embodiments,the gate dielectric layer may include an interfacial layer formed overthe channel region of the fin 204 and a high-K dielectric layer over theinterfacial layer. The interfacial layer of the gate dielectric layermay include a dielectric material such as silicon oxide layer (SiO₂) orsilicon oxynitride (SiON). The high-K dielectric layer of the gatedielectric layer may include HfO₂, TiO₂, HfZrO, Ta₂O₃, HfSiO₄, ZrO₂,ZrSiO₂, combinations thereof, or other suitable materials. In stillother embodiments, the gate dielectric layer may include silicon dioxideor another suitable dielectric. The gate dielectric layer may be formedby chemical oxidation, thermal oxidation, atomic layer deposition (ALD),physical vapor deposition (PVD), chemical vapor deposition (CVD), and/orother suitable methods. In an embodiment, the conductive gate materialis a metal layer. The metal layer may include a conductive layer such asW, TiN, TaN, WN, Re, Ir, Ru, Mo, Al, Cu, Co, Ni, combinations thereof,and/or other suitable compositions. In some embodiments, the metal layermay include a first group of metal materials for N-type FinFETs and asecond group of metal materials for P-type FinFETs. Thus, the device 200may include a dual work-function metal gate configuration. For example,a metal layer (e.g., for N-type devices) may include metals having awork function substantially aligned with a work function of thesubstrate conduction band, or at least substantially aligned with a workfunction of the conduction band of the channel region of the fin 204.Similarly, for example, a metal layer (e.g., for P-type devices) mayinclude metals having a work function substantially aligned with a workfunction of the substrate valence band, or at least substantiallyaligned with a work function of the valence band of the channel regionof the fin 204. Thus, the metal layer(s) may provide a gate electrodefor the FinFET device 200. In some embodiments, the gate electrode ofthe gate structure 208 is provided by a polysilicon layer. The gateelectrode of the gate structure 208 may be formed using PVD, CVD,electron beam (e-beam) evaporation, and/or other suitable process. Insome embodiments, sidewall spacers 302 (see FIG. 3A, 3B) are formed onsidewalls of the gate structure 208. The sidewall spacers 302 mayinclude a dielectric material such as SiO₂, SiN, SiC, SiON, SiOC, SiOCN,SiCN, or combinations thereof. The sidewall spacers 302 may include, insome embodiments, multiple layers.

As discussed above, in some embodiments, the source/drain regions 205,207 are epitaxial source/drain features which may be formed by one ormore epitaxial processes. In some cases, the epitaxial source/drainfeatures 205, 207 may be formed in, on, and/or surrounding the fin 204.For example, in some embodiments, fin 204 is formed extending from thesubstrate 202, and subsequently, the fin 204, at the region of thesource/drain features 205, 207 is etched back to form a trench in thefin 204. The epitaxial source/drain features 205, 207 may be grown inand/or extending from the trench. In other embodiments, the source/drainfeatures 205, 207 may be formed surrounding the fin 204. In someembodiments, such as in a gate-all-around device, portions ofsemiconductor material (e.g., forming the channel of the GAA device) mayextend in the region on and/or between which the source/drain features205, 207 may be formed (e.g., as cladding). In still other embodiments,the fin 204 may be suitably doped to provide the source/drain features205, 207 or portions thereof.

The method 100 then proceeds to block 104 where one or more insulatinglayers are formed over the gate structure and the source/drain features.FIG. 2 illustrates an insulating layer(s) 210 formed over substrate 202such that it is formed adjacent the gate structures 208 and over thesource/drain regions 205/207. The insulating layer 210 may include aplurality of layers such as illustrated in FIGS. 3A/3B. For example, insome embodiments, the insulating layer 210 includes sidewall spacers302, contact etch stop layers (CESL) 304, and inter layer dielectric(ILD) 306. In an embodiment, the ILD 306 is referred to as ILD0 as it isthe lowest of a plurality of ILD layers of multi-layer interconnectstructure formed over the substrate 202. In an embodiment, CESL 304 maycomprise silicon nitride, silicon oxynitride, silicon nitride withoxygen or carbon elements, other suitable materials, or combinationsthereof, and may be formed by CVD, PVD, ALD, other suitable methods, orcombinations thereof.

By way of example, the ILD layer 306 may include a dielectric material,such as tetraethylorthosilicate (TEOS), silicon oxide, a low-kdielectric material, doped silicon oxide such as borophosphosilicateglass (BPSG), phosphosilicate glass (PSG), fluorine doped silicate glass(FSG), boron doped silicate glass (BSG), other suitable dielectricmaterials, or combinations thereof. The ILD layer 306 may include amulti-layer structure having multiple dielectric materials and may beformed by a deposition process such as, for example, CVD, FCVD, PECVD,SOG, other suitable methods, or combinations thereof.

In an embodiment, one or more of the dielectric materials of theinsulating layer 210 may be formed over the gate structures 208 andsubsequently planarized to expose a top surface of the gate structure208. In some further embodiments, after the planarization a dummy gate(e.g., polysilicon) of the gate structure 208 is removed and replacedwith a metal gate electrode forming the gate structure 208. This is canbe referred to as a gate-replacement process.

In some embodiments, block 104 of the method 100 continues to formadditional insulating (dielectric material) layers over the substrateincluding the gate structure and/or source/drain features. In anembodiment, an etch stop layer 308 is formed over the gate structure 208and/or the insulating layer(s) 210. In an embodiment, the etch stoplayer 308 is silicon nitride or other suitable composition. In variousexamples, the etch stop layer 308 may be deposited by ALD, CVD, PVD, orby another suitable method. In an embodiment, another inter layerdielectric (ILD) layer 310 is formed over the gate structure 208 and thesource/drain features 205/207. The ILD layer 310 may be referred to asILD1 and may be disposed above the ILD layer 306 (e.g., ILD0). By way ofexample, the ILD layer 310 may include a dielectric material, such astetraethylorthosilicate (TEOS), silicon oxide, a low-k dielectricmaterial, doped silicon oxide such as borophosphosilicate glass (BPSG),phosphosilicate glass (PSG), FSG, boron doped silicate glass (BSG),other suitable dielectric materials, or combinations thereof. The ILDlayer 310 may include a multi-layer structure having multiple dielectricmaterials and may be formed by a deposition process such as, forexample, CVD, FCVD, PECVD, SOG, other suitable methods, or combinationsthereof. The ILD layers 310 and 306 may include the same or differentcompositions.

As will be appreciated having formed the transistor features such asgate structure 208 and source/drain features 205, 207, it is necessaryto provide a connection to these transistor features such that thedevice 200 can be controlled and interconnected with other devices toform an integrated circuit. As will be appreciated by the discussionbelow, embodiments of the present disclosure offer advantages over theexisting art, though it is understood that other embodiments may offerdifferent advantages, not all advantages are necessarily discussedherein, and no particular advantage is required for all embodiments. Forexample, embodiments discussed herein include structures and methods forreducing a resistance (e.g., on-state resistance), by the etchingoptimization and replacement of source/drain region material duringfabrication of contact features. The methods and devices provided hereincan control contact and series resistance. Various embodiments disclosedherein may also generally be used to improve process control and/orreduce process cost and complexity. Additional embodiments andadvantages are discussed below and/or will be evident to those skilledin the art in possession of this disclosure.

The method 100 then proceeds to block 106 where a portion of thedielectric or insulating layers overlying the source/drain regions areremoved. The removal of the insulating material provides a trenchextending through the dielectric layers reaching and exposing thesource/drain region. The removal is also referred to as forming acontact opening. Referring to the example of FIG. 4A/4B, a trench 402 isetched in the dielectric layers (e.g., ILD 310, ESL 308, ILD 306, CESL304). In some embodiments, a portion of the gate spacers 302 may also beetched (e.g., if a trench 402 is misaligned or the spacing between gatestructures 208 is tight). The trench 402 may be formed by aphotolithography process defining the trench region such as by a maskingelement disposed above the ILD 310, and an etching process defined bythe masking element to form the trench as defined by the maskingelement. While a single trench 402 is illustrated, any number oftrenches are possible. Further, in some embodiments, a trench extendingto contact the gate structure 208 may concurrently formed. In someembodiments, the contact opening to the gate structure is separatelyformed.

In some embodiments, the etching process is a dry etching process thatemploys one or more etchant, such as a fluorine-containing gas (e.g.,C₄F₆, CF₄, SF₆, CH₂F₂, CHF₃, and/or C₂F₆), oxygen, hydrogen, othersuitable gases, or combinations thereof. In some embodiments, theetching process includes a plasma etch. In some embodiments, the etchingprocess is a wet etching process. Combinations of dry (e.g., plasma)etching and wet etching are possible.

In an embodiment, the etching process forming the trench 402 over-etches(e.g., continues past a bottom surface of the insulating layer(s)) andextends into the source/drain region 205, 207 such that the etchingremoves a portion of the semiconductor material of source/drain region205, 207 forming a recess. The over-etching may a by-product of controlof the timed etch, or be purposefully designed into the timed etched. Inan embodiment, the material removed from the source/drain region 205,207 is epitaxially grown semiconductor material such as silicon, silicongermanium, germanium, silicon carbide, or other suitable materials asdiscussed above. In a further embodiment, the material removed issuitably doped epitaxially grown semiconductor material such as, dopedwith boron, phosphorus, arsenic and/or other dopant types including asdiscussed above.

In an embodiment, a depth d1 is removed from the source/drain region205, 207 in forming the trench 402. In other words, the recess formed inthe source/drain region 205, 207 has a depth d1. In an embodiment, thedepth d1 may be between approximately 1 nanometers (nm) andapproximately 20 nm. In a further embodiment, d1 is measured from a gatelevel, or a level coplanar with a bottommost point on the gate structure(e.g., gate dielectric layer such as the interfacial layer). In anembodiment, the depth d1 is between approximately 2% and approximately30% of the thickness source/drain region 205, 207 or its overall,original depth. For example, in an embodiment depth d1 is measured froma bottom surface of the source/drain region 205, 207 epitaxial materialvertically extending to an original top surface of the epitaxially grownmaterial.

The method 100 then proceeds to block 108 where, after the etching ofblock 106, a semiconductor material is formed within trench. Referringto the example of FIG. 5A/5B, a semiconductor material 502 is providedon the source/drain region 205/207. In an embodiment, the semiconductormaterial 502 is deposited within recess of the depth d1 created by theremoval of material the source/drain region 205/207 discussed above inblock 106. In some embodiments, the semiconductor material 502 extendsabove the depth d1 of the recess. As such, the semiconductor material502 has a thickness t1. In an embodiment, t1 is greater than d1. In anembodiment, the thickness t1 of the deposited semiconductor material 502may be between approximately 2 nm and 30 nm in thickness. In anembodiment, the thickness t1 is between approximately 2% andapproximately 30% of the thickness source/drain region 205, 207 or itsoverall, original depth. Including as illustrated in FIG. 5A, in anembodiment, the semiconductor material 502 is grown to a height abovethat of the CESL 304.

In some embodiments, the semiconductor material 502 is selectively grownon the source/drain region 205, 207. The selective growth may includeepitaxial growth from the semiconductor material of the source/drainregion 205, 207 (e.g., as a seed), while material is not grown on thesurrounding insulating layers.

The semiconductor material 502 may be formed by processes where thetemperature is maintained within the allowed thermal budget. In someembodiments, the process temperature to form the semiconductor material502 is less than 500 Celsius. Further exemplary process conditions aredescribed below. In a further embodiment, the semiconductor material 502is grown at a process temperature of 350 C.

In an embodiment, the semiconductor material 502 may be silicon. In anembodiment, the silicon is not purposefully doped. In an embodiment, thesemiconductor material 502 may be formed by epitaxial growth, CVD,PECVD, ALD, PEALD, and/or other suitable process. The precursors of theformation process may include a silicon source, inert materials, and/orother suitable reactive and non-reactive materials. Exemplary precursorsinclude silane, di-silane, di-chloride silane, Hex-c H2, N2, O2, NH3,HF, F2, NF3, Cl2, Ar, He, and/or other suitable precursors. Exemplaryflow rates of the precursors include gas flow rate ranges of betweenapproximately 10 standard cubic centimeters per minute (sccm) andapproximately 20000 sccm. Precursor to carrier gas ratio may be betweenapproximately 0.001 to approximately 0.5. In some embodiments, thetemperature of the process forming the semiconductor material 502 isbetween approximately room temperature (RT) and 700 Celsius. It is notedthat as discussed above, the thermal budget should be accounted for thedetermination of the allowable temperature range. In some embodiments,the pressure of the process forming the semiconductor material 502 isbetween approximately 0.01 and 100 Torr. The epitaxial growth processmay be performed for between about 1 minute and about 30 minutes.

Continuing with the description of various embodiments above, it isunderstood that various parameters of the described deposition processcan be tuned to achieve desired growth characteristics of the silicon(SiGe) material including those parameters discussed above. A flow rateof a deposition gas (including the silicon-comprising precursor gas, thecarrier gas, and/or the etching gas), a concentration (or dosage) of thesilicon-comprising precursor gas, a concentration (or dosage) of thecarrier gas, a concentration (or dosage) of the etching gas, a ratio ofthe concentration of the silicon-comprising precursor gas to theconcentration of the carrier gas, a ratio of the concentration of thesilicon-comprising precursor gas to the concentration of the etchinggas, a ratio of the concentration of the carrier gas to theconcentration of the etching gas, a power of a radiofrequency (RF)source (for example, used during the deposition process to generate aplasma), a bias voltage (for example, applied during the depositionprocess to excite the plasma), a pressure (for example, of a chamber inwhich the deposition process is performed), a duration of the depositionprocess, other suitable deposition parameters, or combinations thereof.These parameters may be selected to provide the suitable concentrationof SiGe (e.g., atomic ratio of silicon and germanium), the tuning thespeed and/or direction to epitaxial growth, tuning the defect density ofthe grown material, and/or other suitable considerations. It is notedthat as this epitaxial material is consumed at least in part with theformation of the silicide (discussed below), certain process parametersmay be relaxed with respect to the growth of epitaxial material forproviding the carrier region of the source/drain.

In some embodiments, a duration of the deposition process, a flow rateof the deposition gas, a temperature of the deposition process, and apressure of the deposition process are tailored to ensure that thesilicon (SiGe) material grows (deposits) more quickly on source/drain Sior SiGe surfaces than oxide surfaces (i.e., sidewall of contracttrench).

In an embodiment, the duration of the deposition process is betweenabout 1 ms to about 10 min. In some embodiments, the deposition processmay include multiple cycles. In an embodiment, a flow rate of thedeposition gas is about 10 sccm (standard cubic centimeters) to about20,000 sccm. As discussed above, the deposition gas can include acarrier gas(es) and one or more precursor gases. In an embodiment, theepitaxial deposition process is performed at a pressure of about 0.01Torr to about 100 Torr. In an embodiment, the deposition process is alow temperature deposition process, for example, performed at atemperature less than about 700° C. In some embodiments, the temperatureis about room temperature (for example, about 20° C. to about 25° C.) toabout 700° C.

In an embodiment of the device 200 (e.g., a pMOS device), thesource/drain region 205, 207 is silicon germanium. In a furtherembodiment, the semiconductor material 502 is silicon and is formed fromthis silicon germanium surface (e.g., seed). In an embodiment of thedevice 200 (e.g., nMOS device), the source/drain region 205, 207 issuitably doped silicon. In a further embodiment, the semiconductormaterial 502 is silicon and is formed from this doped silicon surface(e.g., seed) of the source/drain region 205, 207. In an embodiment ofthe device 200, the source/drain region 205, 207 is germanium. In afurther embodiment, the semiconductor material 502 is silicon and isformed from the germanium surface (e.g., seed). Additional combinationsare possible including those discussed above.

The method 100 then proceeds to block 110 where a liner layer isdeposited within trench, for example, along the sidewalls of the trenchand on the semiconductor material formed in block 108. The liner layermay serve to provide isolation between the subsequently formed contactconductive materials and the surrounding insulating materials. Referringto the example of FIG. 6, a liner layer 602 is illustrated. In anembodiment, the liner layer 602 is silicon nitride. Other exemplarymaterials include those providing a barrier between the subsequentlydeposited metal and the surrounding features. Exemplary thicknesses ofthe liner layer 602 include between approximately 0.5 nm andapproximately 25 nm nanometers. The liner layer may be formed by ALD,CVD, and/or other suitable processes. As illustrated in FIG. 6, theliner layer 602 may be a conformal layer.

The method 100 then proceeds to block 112 where the liner layer,discussed above with respect to block 110, is etched. The liner layermay be etched to expose a surface of the semiconductor materialdeposited above in block 108. Referring to the example of FIG. 7, theliner layer 602 is etched forming opening 702 in the liner layerexposing the semiconductor material 502. In embodiments, the liner layer602 over the ILD layer 310 is also removed. The liner layer 602 may beetched by a selective etch. Exemplary etches include wet etch and/or dryetches (e.g., plasma etching).

In some embodiments, a degree of over-etch is also experienced in theetching of block 110. Thus, the etching extends into the semiconductormaterial 502 removing a portion of the semiconductor material 502forming a recess. As illustrated in FIG. 7, a depth d2 is removed fromthe semiconductor material 502. In other words, in an embodiment, therecess has a depth d2. In an embodiment, the depth d2 is betweenapproximately 0 nm and approximately 10 nm. In a further embodiment, thedepth d2 is approximately 2 nm. In an embodiment, d2 is less than d1. Inan embodiment, d2 is less than t1.

The method 100 then proceeds to block 114 where a first metal layer isformed. The first metal layer is formed within the trench. The firstmetal layer may be a silicide region formed by converting thesemiconductor material formed in block 108. In some embodiments, thefirst metal layer is formed by a silicidation process targeting andconverting the silicon of semiconductor layer provided in block 108 tosilicide. The silicidation process may include depositing a metalcomposition over the semiconductor material (e.g., 502) and annealingthe structure to form a metal silicide. In some embodiments, thesilicide layer includes a metal silicide, such as nickel silicide,cobalt silicide, tungsten silicide, tantalum silicide, titaniumsilicide, platinum silicide, erbium silicide, palladium silicide, othersuitable silicides, or combinations thereof. Thus, exemplary metalsformed over the semiconductor material (e.g., silicon) include nickel,cobalt, tungsten, tantalum, titanium, platinum, erbium, palladium,and/or other suitable metals.

Referring to the example of FIG. 8, the silicide region 802 is formed.The silicide region 802 may consume the semiconductor material 502 inits entirety. In some embodiments, a portion of the source/drain region205, 207 underlying the semiconductor material 502 is also consumed toform the silicide region 802. In an embodiment, the silicide region 802is titanium silicide (TiSi). However, other suitable silicidecompositions are possible. As discussed above, in some embodiments, thesilicide region 802 may be formed by a deposition process such as CVD,ALD, PVD, other suitable processes, or combinations thereof of a metalmaterial. The deposited metal layer (e.g., titanium) is formed over andinterfacing the semiconductor material 502. Then, the device 200 isannealed to allow the metal and the semiconductor material 502 and/orthe source/drain region 205, 207 to react forming silicide. Thereafter,the un-reacted metal layer is removed, leaving the silicide region 802over the source/drain regions 205, 207.

The method 100 then proceeds to block 116 where a second metal layer(s)is deposited. In some embodiments, one or more conductive layers aredeposited such that the remained of the contact opening is filled. Thesecond metal layer(s) may be referred to a contact metal(s). Asillustrated in FIG. 9, contact metal layer 902 may be deposited withinthe trench 402 and interfacing the silicide region 802 over thesource/drain regions 205, 207 such that metal layer 902 provides anelectrical connection, through the silicide region 802, to thesource/drain features 205/207. In at least some examples, the contactmetal layer 902 includes a Co layer. In some examples, the contact metallayer 902 includes tungsten W. However, other suitable metals orcombinations thereof may be used without departing from the scope of thepresent disclosure including, for example, Ru, Cu, Ta, Ti, Al, Mo, andthe like. In some cases, the metal layer 902 may be deposited by PVD,e-beam evaporation, CVD, ALD, plating, or other appropriate method. Themetal layer 902 may be multi-layer structure. After deposition of themetal material, a CMP process in block 118 may be performed removing thematerial from over the ILD layer 310 and providing a planar surface ofthe metal layer 902 and the ILD layer 310.

The method 100 may proceed to perform additional processing steps inblock 120. In some embodiments, additional layers are formed, forexample, prior to forming the metal layer 902. For example, adhesionlayers may be formed on the trench 402 prior to deposition of the metallayer 902. The adhesion layer 904 is illustrated in FIG. 9. Examplematerials for the adhesion layer 904 include various conductivematerials such as TiN, TaN, and/or other suitable materials.

The contact metal layer 902 (and adhesion layer 904) and the silicideregion 802 may together be referred to a contact element or contact viaelement. The contact element provides electrical connection to thesource/drain regions 205, 207. While a single contact is shown in FIG.9, numerous contacts may be formed to respective ones of thesource/drain regions 205/207 and also contact elements may be formed tothe gate structure 208 (not shown).

The device 200 may undergo further processing to form various featuresand regions known in the art. For example, subsequent processing mayform various contacts/vias/lines and multilayer interconnect features(e.g., metal layers and interlayer dielectrics) on the substrate,configured to connect the various features to form a functional circuitthat may include one or more FET (e.g., FinFET) devices. In furtheranceof the example, a multilayer interconnection may include verticalinterconnects, such as vias or additional contacts, and horizontalinterconnects, such as metal lines. The various interconnection featuresmay employ various conductive materials including copper, tungsten,silicide, cobalt, and/or other conductive materials. In one example, adamascene and/or dual damascene process is used to form a copper relatedmultilayer interconnection structure.

FIGS. 10 and 11 are illustrative of forming additional layers of amultilayer interconnect (MLI) including forming additional etch stoplayer 1002 and ILD layer 1004 (e.g., referred to as ILD2). The ILD layer1004 may be substantially similar to the ILD layer 306 and/or ILD layer310 discussed above. The ILD layer 1004 may be similarly composed as ILDlayers 306 and/or 310 or have a different composition. The etch stoplayer 1002 may be substantially similar to as discussed above withreference to the layer 308. The layers 1002 and 308 may have similarcompositions, or differing compositions.

Openings are then etched in the etch stop layer 1002 and ILD layer 1004by suitable wet and/or dry etching for example, as defined by alithography patterning process. The openings may define a metalinterconnect feature such as a metal line, providing a horizontalrouting of an electrical signal. The openings are then filled withconductive material(s) as illustrated by conductive element 1102 of FIG.11. Conductive element 1102 may be a single layer or multi-layers.Exemplary compositions include copper, aluminum, polysilicon, and/orother suitable materials. The conductive element 1102 may be formed bydeposition processes including CVD, ALD, PVD, plating, and/or othersuitable methods. Additional interconnect layers may be formed over andelectrically coupled to the conductive element 1102.

Referring now in particular to FIGS. 3B, 4B, and 5B illustrated thereinis an illustration of an embodiment of the device 200, a device 200′,which may be fabricated in a manner substantially similar in manyrespects as discussed above. Thus, many aspects of the description ofthe method 100, with respect to the device 200, also apply to the device200′. For example, the illustrations and discussions of FIGS. 6-11similarly apply to the device 200′ with differences in source/drainconfiguration noted here. The differences in device 200′ is that the topsurface of the source/drain region 205/207 is not necessarily aligned atop of the substrate, fin or bottom of the gate structure 208. Thus,while the same method steps and features are provided, FIGS. 3B, 4B, and5B illustrate that in an embodiment, the source/drain 205/207 is aso-called raised source/drain. The over-etch of d1 may still beprovided, but that depth is defined by the original height of thesource/drain region and may not be aligned with a plane of the bottom ofthe gate. Note that the remaining process steps are substantiallysimilar to as discussed above. That is, that additional material (block108 as exemplified by semiconductor material 502) is provided within theover-etch recess of the source/drain 205/207.

Thus, provided herein are methods and devices that, in some embodiments,provide for replacement of a recessed portion of the source/drainmaterial by depositing an additional semiconductor material within atrench. The additional semiconductor material allows for consumption ofthe additional semiconductor material to form a silicide with lessimpact to the functional source/drain (e.g., less consumption of thedoped source/drain to form the silicide). The methods may, as discussedabove, allow for in some embodiments an improvement in the on-stateresistance of the device by reducing the contact resistance.

Thus, the various embodiments described herein offer several advantagesover the existing art. It will be understood that not all advantageshave been necessarily discussed herein, no particular advantage isrequired for all embodiments, and other embodiments may offer differentadvantages. For example, embodiments discussed herein include structuresand methods for reducing resistance, protecting against source/drainloss and providing source/drain contact, among others, and therebyimproving device performance. In some embodiments, methods are provided,which may be used to provide form additional semiconductor materialavailable for silicide formation over-consumption of the source/drainfeature. Additional embodiments and advantages will be evident to thoseskilled in the art in possession of this disclosure.

Thus, one of the embodiments of the present disclosure described amethod that includes providing a gate structure and a source/drainfeature adjacent to the gate structure. An insulating layer or layersare formed over the source/drain feature. A trench is formed (e.g.,etched) in the insulating layer to expose a surface of the source/drainfeature. A semiconductor material is formed in the etched trench on thesurface of the source/drain feature. The semiconductor material is thenconverted to a silicide.

In a further embodiment of the method, a contact metal layer is formedover the silicide filling the etched trench. In an embodiment, thesemiconductor material includes forming silicon on the surface of thesource/drain feature. For example, in some embodiments, the source/drainfeature is epitaxially grown prior to forming the dielectric layer. In afurther embodiment, the epitaxially growing the source/drain featureincludes epitaxially growing silicon germanium.

In an embodiment, the method further includes forming a liner layer onsidewalls of the etched trench after forming the semiconductor material.The liner layer may be formed before converting the semiconductormaterial to the silicide. In an embodiment, the method also includesetching the formed liner layer. The etching the formed liner layer canremove a portion of the formed liner layer and remove a portion of thesemiconductor material.

In an embodiment, the method includes etching the trench in theinsulating layer by etching a recess into the source/drain feature. In afurther embodiment, the semiconductor material is formed in the recess.

In another of the broader embodiments discussed herein, a methodincludes providing a device including a gate structure and asource/drain feature adjacent to the gate structure. An insulating layer(including insulating layers) are formed over the source/drain feature.A contact opening is etched in the insulating layer, the etching forms arecess in the source/drain feature under the contact opening. Silicon isthen deposited in the recess. The silicon can then be converted tosilicide. The remaining contact opening is filled with contact metal toform a contact element to the source/drain feature.

In a further embodiment, the method includes depositing the silicon byselectively depositing the silicon on an exposed surface of the recessof the source/drain feature. For example, in an embodiment, the siliconis selectively deposited by epitaxially growing the source/drain featureof at least one of silicon germanium, silicon carbide, or germanium. Inan embodiment, forming the insulating layer over the source/drainfeature includes forming an interlayer dielectric (ILD) layer overlyinga contact etch stop layer (CESL); the ILD layer and the CESL cancomprise a different dielectric composition. In an embodiment, themethod includes converting the silicon to silicide by converting aportion of the source/drain feature to silicide.

In an embodiment, the silicon is deposited in the recess withoutpurposefully doping the silicon. In an embodiment, the method includesforming a liner layer over the silicon and sidewalls of the contactopening. The liner layer is then etched to expose the silicon. Etchingthe liner layer also etchings a second recess in the silicon.

In another of the broader embodiments discussed herein a semiconductordevice is provided. The device includes a source/drain region adjacent agate structure on a semiconductor substrate; an insulating layer formedover the substrate and having an interface with a top surface of thesource/drain region; and a contact element extending through theinsulating layer to the source/drain region. The contact element furtherincludes a silicide region having a substantially U-shape incross-section, such that the silicide region extends above theinterface; and a metal contact layer over the silicide region and withinthe U-shape.

In a further embodiment, the device includes the silicide region of TiSiand the source/drain region is SiGe. In an embodiment, the devicefurther includes a liner layer disposed along a sidewall of the metalcontact and interfacing a top surface of the U-shaped silicide region.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: providing a deviceincluding a gate structure and a source/drain feature adjacent to thegate structure; forming an insulating layer over the source/drainfeature; etching a trench in the insulating layer to expose a surface ofthe source/drain feature; forming a semiconductor material in the etchedtrench on the surface of the source/drain feature; forming a liner layeron sidewalls of the etched trench after forming the semiconductormaterial; and converting the semiconductor material to a silicide. 2.The method of claim 1, further comprising: forming a contact metal layerover the silicide filling the etched trench.
 3. The method of claim 1,wherein the forming the semiconductor material includes forming siliconon the surface of the source/drain feature.
 4. The method of claim 3,further comprising: epitaxially growing the source/drain feature priorto forming the insulating layer.
 5. The method of claim 4, wherein theepitaxially growing the source/drain feature includes epitaxiallygrowing silicon germanium.
 6. The method of claim 1, wherein the formingthe liner layer is performed before converting the semiconductormaterial to the silicide.
 7. The method of claim 1, further comprising:etching the formed liner layer, wherein the etching the formed linerlayer removes a portion of the formed liner layer and removes a portionof the semiconductor material.
 8. The method of claim 1, wherein theetching the trench in the insulating layer includes etching a recessinto the source/drain feature.
 9. The method of claim 8, wherein theforming the semiconductor material forms the semiconductor material inthe recess.
 10. A method, comprising: providing a device including agate structure and a source/drain feature adjacent to the gatestructure; forming an insulating layer over the source/drain feature;etching a contact opening in the insulating layer, wherein the etchingremoves a portion of the insulating layer and a portion of thesource/drain feature to form a recess in the source/drain feature underthe contact opening; after etching the contact opening in the insulatinglayer and the source/drain feature, depositing a silicon layer in therecess and on a top surface of the etched source/drain feature; andconverting the silicon layer to silicide and filling the contact openingwith contact metal to form a contact element to the source/drainfeature, wherein the converting the silicon layer to silicide includesconverting a portion of the source/drain feature to silicide.
 11. Themethod of claim 10, wherein the depositing the silicon layer includesselectively depositing the silicon layer on an exposed surface of therecess of the source/drain feature.
 12. The method of claim 11, furthercomprising: epitaxially growing the source/drain feature of at least oneof silicon germanium, silicon carbide, or germanium.
 13. The method ofclaim 10, wherein the forming the insulating layer over the source/drainfeature includes forming an interlayer dielectric (ILD) layer overlyinga contact etch stop layer (CESL), wherein the ILD layer and the CESLcomprise a different dielectric composition.
 14. The method of claim 10,wherein the converting the silicon layer to silicide includes convertingan entirety of the silicon layer to the silicide.
 15. The method ofclaim 10, wherein the depositing the silicon layer in the recessincludes not purposefully doping the silicon layer.
 16. The method ofclaim 10, further comprising: forming a liner layer over the siliconlayer and sidewalls of the contact opening; and etching the liner layerto expose the silicon layer, wherein the etching the liner layer alsoetchings a second recess in the silicon layer.
 17. A method, comprising:providing a device including a gate structure and a source/drain featureadjacent to the gate structure; forming an insulating layer over thesource/drain feature; etching an opening in the insulating layer,wherein the opening extends into the source/drain feature; depositingsilicon in a bottom portion of the opening; forming a liner layer alongsidewalls of the opening and over at least a portion of the depositedsilicon; converting the silicon to silicide; and depositing a metallayer in a top portion of the opening to form a contact element to thesource/drain feature.
 18. The method of claim 17, wherein the providingthe device including the source/drain feature includes: growing a raisedsource/drain feature extending above a top surface of a semiconductorsubstrate.
 19. The method of claim 17, wherein after the converting thesilicon to silicide, a portion of the silicide interfaces the linerlayer.
 20. The method of claim 17, wherein the depositing siliconincludes epitaxially growing undoped silicon.